The present invention relates to a device for changing the position of an optical imaging system. Such optical imaging systems are preferably disposed between an object, e.g. a visual display endoscope, and a camera unit.
The application of video cameras in biomedical engineering, which are employed particularly in combination with endoscopes for observing intracorporeal regions, has been known for quite a time. The video technology introduced in biomedical engineering permits the display of minute intracorporeal regions on a monitor and hence allows for an enlarged display of the region to be treated for observation. Additionally it provides an opportunity for several persons to follow up a surgical operation, at least visually. Compliance with the high demands in terms of sterilization, which are common in surgery, requires a maximum of sterilization of the instruments used in a video-assisted endoscopic surgical operation, However, this is a requirement which neither of interest in common recording and video engineering nor has so far been considered in the design and implementation of such equipment. The "endoscope video systems" employed in biomedical engineering are composed of an observation endoscope which is connected by means of a coupler, e.g. of the type described in the German Patent 37 10 648 C2, via an optical imaging system to a video camera unit. The demands on sterilization of the common endoscopes and, on account of their technological designs, the video cameras currently on the market comply with today's medical standards which require easy sterilizability.
The optical imaging systems so far employed, which serve to focus the intracorporeal regions under observation by means of a visual endoscope sharply onto the imaging plane located in the video camera, include mechanical adjusting mechanisms which permit a displacement of the optical imaging system along the optical axis. Such adjusting mechanisms generally consist of a small focusing lever provided on the outer wall of a casing which accommodates the optical imaging system. Appropriately engaging and intermeshing gears or worm gear threads may be provided for the axial adjustment of the optical imaging system, which is arranged inside the casing, by tilting the outside focusing lever for adjustment inside the casing. This requires, however, at least one drive shaft extending through the casing wall. For compliance with the requirement of sterile conditions it is necessary to ensure appropriate sealing provisions so as to prevent any liquid from penetrating into the interior space of the casing which houses the optical imaging system. To this end the penetrating ducts must be provided with suitable seals in particular, through which passes the connecting shaft between the focusing lever and an adjusting mechanism for adjustment of the position of the optical imaging system.
Apart from expensive and complex sealing provisions, which are indispensable in the known adjusting mechanisms for focusing of the optical imaging system, there is the further disadvantage of wear of these seals, which are subject to a permanent removal of material due to friction caused by the focusing movement so that such sealing provisions need maintenance and replacement after a certain time.
Another disadvantage of the known adjusting mechanisms for changing the position of the optical imaging system, which may also consist of a solid housing element and an adjusting ring for instance e.g. of the type common from the field of photographic lenses, resides in their poor operating and handling characteristics, as with such adjusting mechanisms a single-handed operation is extremely troublesome, if not entirely impossible, and demands a great deal of adaptation and habituation. Moreover the known adjusting mechanisms do not provide any symmetry for left-handed and right-handed operation.